(CNN) On the banks of the Rio Grande near the south Texas city of Hildalgo, dozens of undocumented migrants -- mostly women and young children -- descended a hill on the Mexican side of the border in an orderly procession.
The sun set Thursday over an all-too-familiar portrait of desperation in the the Rio Grande Valley. Some women carried wailing babies while others hauled bags of belongings to the edge of the muddy river, where a group of men awaited them with life vests to take turns crossing from Mexico to the United States. That day alone, authorities said, 2,000 migrants were apprehended in the valley.
"From Honduras," several migrants shouted at a CNN correspondent who asked where they were from. Some had been traveling for months -- fleeing violence, poverty and the destruction wrought by a pair of hurricanes, they said. CNN observed the raft make about half a dozen trips across the river.
"We come for a new opportunity," said one man, who traveled with his wife and young daughter.
The scene reflects a surge of migrants, particularly children, challenging the new administration of President Joe Biden, who entered office promising to reverse the hardline policies of his predecessor.
US officials have attributed this surge in part to instability in the region, exacerbated by the pandemic, and perceptions among migrants of more welcoming immigration policies under a new president.
Roxana Rivera, 28, said she and her 6-year-old daughter left Honduras after back-to-back November hurricanes destroyed her home and everything in it.
Word back home, Rivera said, was that the US was now allowing people with children to freely cross the border -- which wasn't entirely true. She heard that on the news, she said. Relatives in the US relayed the same information. Other migrants had similar stories.
Rivera said she was elated when the group she crossed the border with -- mostly mothers and their children -- was picked up by border agents. The migrants were processed, then taken to a bus station in Brownsville, Texas, where they were tested for Covid-19 and offered supplies by nonprofits before their release. She planned to stay with relatives in Houston while her immigration case is processed.
"You always dream about living in a house with your children," said Rivera, becoming emotional. "Now we have nothing ... We dream of having a house."
Rivera said she at times regretted embarking on the long journey north by foot and by train -- putting her daughter's life at risk. Sometimes the girl would ask for food and she had none to offer her. One time, she said, her daughter became dehydrated. Another time she had to seek medical attention in Mexico when her daughter had a fever.
Maria Mendoza, a 30-year-old migrant from El Salvador, appeared exhausted as she arrived in Brownsville after processing by immigration officials. She was hoping to reunite with relatives who live in Maryland, she said through tears.
Mendoza recalled that the raft she and others used on a midnight crossing of the Rio Grande flipped over, sending several mothers and their children into the water. She said there were days when she did not eat so that her 6-year-old daughter would not go hungry. Her daughter remembered evading a snake along the way.
"More than anything I want to be reunited with my family," she said. "We want to make a life here. A better future for our children."
Authorities have arrested and encountered more than 100,000 migrants on the border over a four week period ending on March 3, according to data obtained by CNN. The surge marks the highest levels for the same time frame in five years.
Border agents are encountering 4,000 to 5,000 people daily, according to a Homeland Security official.
"We're crowded," said Chris Cabrera, a spokesman for the National Border Patrol Council, which represents Border Patrol agents. "We're overcrowded. We don't have anywhere to put people."
He added, "We have them in our custody and the system has bogged down and there's no place for us to send them."
Unaccompanied migrant children are another part of the administration's problem.
On Wednesday, the number of unaccompanied children in Border Patrol custody reached more than 3,700, CNN has learned. Many are held in jail-like facilities along the border.
The Border Patrol on Wednesday apprehended nearly 800 unaccompanied migrant children -- surpassing the current 450 daily average, according to a Homeland Security official.
About 8,800 unaccompanied children are in US Health and Human Services custody, the department confirmed Thursday, up from about 7,700 the previous week.
Roberta Jacobson, Biden's coordinator for the southern border, said the administration's message to migrants is now is not the time to come.
"It's really important that people not make the dangerous journey in the first place, that we provide them with alternatives to making that journey, because it's not safe en route," she said Wednesday.
"And so, you know, if I could just emphasize ... that it's really important that that message get out, because the perception is not the same as the reality in terms of the border not being open."
Jacobson reiterated the administration's message: "The border is not open." She said Trump administration immigration policies "intentionally made it worse."
"We can't just undo four years of the previous administration's actions overnight," said Jacobson, adding that it will take "significant time to overcome" the effects of Trump immigration policy.
Still, the new administration's handling of the situation has drawn criticism from Republicans and some Democrats.
Other than unaccompanied children awaiting immigration cases, the Biden administration has continued to turn away most migrants. Some families are admitted into the US on a case-by-case basis. A change in Mexican law banning the detention of small children has prevented US immigration agents from turning away migrant families.
In Brownsville, Sandra, 38, said she fled Honduras after years of threats from a family member. Her full name is not being published because she is a victim of domestic violence. One day, she said, the relative showed up at her house with a gun and opened fire. One of her sons and other family members tackled the man and prevented him from killing her.
She lived with her son in a tent city on the Mexican side of the border last year -- where she taught kindergarten students -- and now awaits an asylum case in the US.
For now, a woman who runs a Brownsville charity has opened her home to Sandra and her young son. She learned this week that she has an immigration hearing in June. Wiping away tears, Sandra said will never return to Honduras.
"I had to leave for good," she said. "I cannot live in my country."